Aircraft heater



June 9, 1942.

` H; J. DE. N. MocoLLUM ummm HEATER Filed Feb.- 1v, 1940 A mush wuwmbu,v Q N\ fw. "my,

Patented June 9,

UNITED STATES PATENT oFFlCE l l Amoazszrzsran y. i

Henry J. De N. McCollum, Chicago, lll. o Application February 17, 1940,serieu No. 319,557

(ol. 23u-12.3)

6 Claims.

., the general practice to secure the necessary suction to draw thecombustible mixture into the heater and to withdraw the products ofcombustion therefrom by making a connection to the intake manifold ofthe automobile engine. If the l engine carburetor is very carefullyadjusted so as to secure maximum emciency in-the operation of theengine, the discharge of the products of combustion from the heater intothe intake manifold may cause the engine to operate less efiiciently ormay make it necessary to readjust' the engine carburetor to makeallowances for the admixture of the heater combustion gases with themixture flowing through the intake manifold. To obviate the necessity ofmaking such adjustments, the heater of the present inventionis adaptedto have its discharge conduit connected to the engine exhaust conduit,and tosecure the necessary flow through the heater, a Venturi-typenozzle is inserted in the engine ex haust pipe and the heater dischargeconduit connected to the throat ofthe nozzle. `In thisway, theperformance of the engine is not materially affected since the Venturirnozzle will not raise the engine exhaust back pressure perceptibly.

Furthermore, in adapting the heater for use on aircraft, it isin someinstances undesirable to introduce the products of combustion from theheater into the intake manifold of the engine. Therefore, in applyingthe heater to some types of aircraft, the suction is preferably producedeither by connection of the discharge pipe of the heaterv to a Venturishaped. passageway located in the exhaust pipe of the engine, or byconnecting the discharge pipe of the heater to a trailing pipe locatedabove the wing at a point at whicha partial vacuum is present. Since itis also very desirable to reduce as much as possiblev the number ofparts of the heater,\when it is installed upon airplanes, the fuelsupply- *for theheater is preferably obtained from the 1 discharge ofthe engine supercharger, the fuel o being thus pre-mixed with the properamount of i air to assure complete combustion.

It is thus an object of my invention to provide an improved vehicleheater of the internal como bussen type 1h which the new through theheater is obtained by the aspirating effect of a Venturi nozzle locatedinthe vehicle engine exhaustpipe.A

A further object is to provide an improved heating system for the cabinsof aircraft.

A further object is to provide an improved heater for use on aircraftVin which a portion ofthe fuel mixture normally supplied to the engineis burned vinthe heater and in which the withdrawal of the products ofcombustion from the heater is caused by a partial vacuum produced eitherin the engine exhaust pipe or by a pipe trailing from the body of theairplane.

A further object is to provide an improved internal combustion typeheater installation for aircraft employing a simplified control meansand embodying features contributing to certain and vsafe operation, l

Other objects will appear from the following description, referencebeing had to the accompanying drawing, which is a diagrammatic .viewofan internal combustiontype heater system as installed upon an airplane.

In utilizing the heater for heating the cabins of v aircraft, theheatercasing 10 is mounted within the cabin 1,2, the heater beingprovided`with the usual combustion chamber casting 14 and having withinthe casing 10 the usual heat exchange device or radiator, together witha motor driven fan for circulating air past the radiator. The heaterwill have the usual-electrical igniter, the operation of which will becontrolled by a thermostatic switch, so as to disconnect the igniterfrom the source of current when the radiator appreaches substantiallyits normal operating temperature. In the drawing the heater III isillustrated as being supplied with current from a source 16 through aswitch which is manually operated by a control button 80, the'controlbutton having a stem 82 which engages one arm of the switch 18 to openthe switch when the control button-is pushed to the right and whichpermits the switch to 'close when the control button is in theposition-in which it is shown in full lines. g

'I'he supply of the combustible mixture of' fuel and air for the heateris derived from the engine 2 2,285,672 v v A fuel mixture supply througha conduit III. one

end of which is connected to the combustion chamber casting 'Il and theother end of which terminates in an elbow 86 located in the outlet pipe88 of the engine supercharger Sli which derives a mixture of fuel andair from the engine carburetor 92. A valve 94 is located in the conduitIl adJacent the end thereof which extends into the pipe 8l, the valvebeing connected for manual operation by the control button 80 through aBowden wire Si or through any other suitable operating connection, thevalve being so arranged as to be open when the control button 80 ismoved to the left, in its full lin'e position, and to be closed vwhenthe control button is moved to its dotted line position. The conduit 84is preferably wrapped with a thermally insulating material so thatshould this conduitbe broken due to vibration or accident, theinsulating material will tend to hold the portions of the conduit at thefracture in juxtaposition and prevent rapid leakage of the fuel from thecon- A duit. Since the elbow I8 faces the supercharger St, the mixtureof air and fuel will be forced into the conduit u under pressure, and itis for this reason that it is desirable to provide the insulatingmaterial around the conduit I4 as well as to locate the ,valve 94closely adjacent the supercharger outlet pipe 08.

The products of combustion from the heater are discharged through aconduit 98 which, by means of a two-way valve IUI may communicate with aconduit 98a or a conduit 98h. The conduit Ola terminates in an elbow |02located at the throat of a Venturi-shaped passageway formed in thenozzle IM located in the engine exhaust pipe |08. The conduit 98hextends through the wing |08 of` the airplane to the upper surfacethereof at the point at which the air pressure is less than atmosphericwhile the piane is in flight. The conduit Sl as well as its extensions98a and 98h are covered with a sultable thermal insulation so that theproducts of combustion from the heater passing therethrough will retainsuicient heat to prevent the formation of ice at the trailing extremityof the conduit 98h or at any place within the conduit 9|. 88a, or 8b. Itwill be understood that if the conduit 08 or its' extensions 98a or bwere exposed to cold air, the water vapor, constituting a large partofthe products of combustion from the heater, might condense and freezein this' the conduit 98a, or the valve I, in which case the conduit 98hmay be formed integrally with or as an extension of the conduit ll. Thevalve I", if utilized, is preferably positioned in a place such that thepilot may operate it by means of its handle IUI. With the particularvalve illustrated, it will be apparent that the conduit 08 may beconnected either to the conduit Ila or to the conduit 98h, or may beconnected to both of these conduits.

'rne heater-.instalation shown may be used 'I5 on airplanes havingsuperchargedV cabins, in which casethe pressure within thev cabin willnormally be greater than that within the combustion chamber and radiatorof the heater so that an accidental leak in the combustion cham- 10' orradiator without any harmful result.

For the heating of large cabin airplanes, a plurality of heater unitsmay be suitably located within the cabin, in which event two or more ofthe units may be supplied with a fuel mixture through a common conduit,such as 8l, and the products of combustion drawn from two or more of theunits through a common discharge conduit, such as 98. In such multipleunit installations, it is of course desirable that -the conduits 8l andll. and their connections on the unit, be

of such character that the flow rate through the units will besubstantially the same and one unit will not receive the combustiblemixture atan excessive rate at the expense of the supply of the mixtureto other units.

To cause operation of the heater, the pilot will pull the ycontrolbutton from the dotted-line to the full-line position shown in thedrawing, thus closing the switch Il and opening the valve 94.

` Thereupon, the igniter which is locatedfin the combustion chambercasting 14 will become energized and ignite the mixture `forced into theconduit 84 by the supercharger `9II. After the casting 'Il or theradiator connected thereto becomes heated to substantially its normaloperating temperature, the igniter circuit will be opened by athermostatically operated switch in the usual manner, Depending upon theposition of the valve |00, which maybe manually conm trolled by thepilot, the products of combustion from the heater unit will be drawninto the exhaust gases flowing throughr the engine exhaust pipe throughthe conduit lla, or will be drawn through the conduit Nb `because of thesubatmospheric pressure at theoutlet of. this pipe due to the shape ofthe wing surface and due also to the iiow of air past the trailingextremity of this conduit. The heater will thus continue in operationuntil the control button l0 is moved 6 from the position in which it isshown in full lines to its dotted line position, whereupon the switch'18 willfbe opened and the valve Il closed.

The usual motor driven fan will be located withinthe casing III tocirculate the air in the cabin 12 past the heater radiator in the usualmanner,

and the opening of the switch 'IB will likewise open the circuit to themotor driving the fan in a manner well known in the art.

While I have shown and described a particular embodiment of myinvention, it will be apparent to those skilled in the art thatvariationsl and modifications thereof may be made without departing fromthe underlying principle thereof. I therefore desire, by the followingclaims,I to

include within the scope of my invention all such similar and equivalentconstructions whereby substantially the results of my invention vmay beobtained by substantially the same o r equivalent means. f`

I claim:

combustion engine, a carburetor, and a supercharger for supplying acombustible mixture of l. In an airplane having a cabin, an internal inthe cabin for heating the air therein, a conduit leading from a pointwhere combustible mixture is maintained under pressure by saidsupercharger to said heater unit to supply a combustible mixturethereto, and a heater discharge conduit leading from said heater unit toa point on the outer surface of said' airplane at which the pressure isless than atmosphericpressure.

2. In an airplanehaving a cabin, an internal.

combustion engine, a carburetor, and a supercharger 'for supplying a'combustible mixture of fuel and air to the engine, the combination ofan internal combustion type heater unit located in the cabinfor heatingthe air therein, a conduit leading from a point at which combustiblemixture is maintained under pressure by said supercharger to said heaterunit to supply av vcombustible mixture thereto, and` means for aidingthe ow of fluid through said heater unit, comprising a dischargeconduit, a nozzle in the engine discharge pipe, said nozzle having aVenturi-shaped passageway extending therethrough, anda connectionbetween said discharge conduit and the vthroat of said Venturi-shapedpassageway.

3. In an airplane having a cabin, an internal combustion engine, acarburetor, vand a supercharger for supplying a combustible mixture offuel and air to the engine, the combination of an internal combustiontype heater unit located in the cabin for heating the air therein, aconduit leading from a point where combustible mixtureis maintained at apressure above atmospheric by said supercharger to said heater unit tosupply a combustible mixture thereto, and means to aid the flow offluids through said heater unit, comprising a discharge conduit leadaspace maintained at subatmospheric pressure by the motion of saidairplane, and means to thermally insulate said discharge conduit tomaintain the temperature of the products of combustion flowingtherethrough above freezing temperature.

ing from said heater unit to a point adjacent a.

5. In a heater for the cabin of an airplane powered by a superchargedinternal combustion.

engine, the combination of a heater vunit of the duit means to convey acombustible mixture of fuel and air to said heater unit from a point atwhich said combustlblemixture is maintained at a pressure aboveatmospheric by the engine supercharger and a manually operated valvelocated close to the supercharger for controlling the flow of thecombustible mixture through said conduit means.

6. In an internal combustion -heating system for the passengercompartment of an airplane powered by aninternal combustion enginehaving a supercharger, the combination of an internal combustion heaterarranged to heat a passenger compartment of the airplane, conduit meansfor supplying combustible .mixture to the heater from a point in theengine combustible mixture supply system between the supercharger andthe engine, a first passageway for discharging the products ofcombustion from said heater to a point in the engine exhaust system, asecond passageway for discharging the products of combustion to a spacemaintained at subatmospheric pressure by the motion of the airplane, andmeans selectively operable to cause the discharge of the products ofcombustion from said heater to either of said passageways.

HENRY J. DE N. MCCOLLUM.

